1. International Workshop on Linear Colliders, 18 – 22 Oct. 2010, CERN, Switzerland 1 Recent progress on CLIC_DDS Roger M. Jones Cockcroft Institute and The University of Manchester International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland

2. International Workshop on Linear Colliders, 18 – 22 Oct. 2010, CERN, Switzerland 2  Roger M. Jones (Univ. of Manchester faculty)  Alessandro D’Elia (Dec 2008, Univ. of Manchester PDRA based at CERN)  Vasim Khan (PhD student, Sept 2007)  Part of EuCARD ( European Coordination for Accelerator Research and Development) FP7 NCLinac Task 9.2  Collaborators: W. Wuensch, A. Grudiev, I. Syrachev, R. Zennaro, G. Riddone (CERN) 2. FP420 –RF Staff Wake Function Suppression for CLIC -Staff V. Khan, CI/Univ. of Manchester Ph.D. student A. D’Elia, CI/Univ. of Manchester PDRA based at CERN (former CERN Fellow).

3. International Workshop on Linear Colliders, 18 – 22 Oct. 2010, CERN, Switzerland 3 Overview Three Main Parts: 1.Review of salient features of manifold damped and detuned linacs. 2.Initial designs (three of them).  CLIC_DDS_C. 3.Further surface field optimisations  CLIC_DDS_E(R). 4.Finalisation of current design. Based on moderate damping on strong detuning. Single-structure based on the eight-fold interleaved for HP testing  CLIC_DDS_A 5.Concluding remarks and future plans.

4. International Workshop on Linear Colliders, 18 – 22 Oct. 2010, CERN, Switzerland 4 1. Introduction –Present CLIC baseline vs. alternate DDS design  The present CLIC structure relies on linear tapering of cell parameters and heavy damping with a Q of ~10.  Wake function suppression entails heavy damping through waveguides and dielectric damping materials in relatively close proximity to accelerating cells.  Alternative scheme, parallels the DDS developed for the GLC/NLC, entails: 1. Detuning the dipole bands by forcing the cell parameters to have a precise spread in the frequencies –presently Gaussian Kdn/df- and interleaving the frequencies of adjacent structures. 2. Moderate damping Q ~ 500-1000

5. International Workshop on Linear Colliders, 18 – 22 Oct. 2010, CERN, Switzerland 5 High power rf coupler HOM coupler Beam tube Acceleration cells Manifold 1. Features of CLIC DDS Accelerating Structure  SLAC/KEK RDDS structure (left ) illustrates the essential features of the conceptual design  Each of the cells is tapered –iris reduces (with an erf-like distribution –although not unique)  HOM manifold running alongside main structure removes dipole radiation and damps at remote location (4 in total)  Each of the HOM manifolds can be instrumented to allow: 1) Beam Position Monitoring 2) Cell alignments to be inferred

6. International Workshop on Linear Colliders, 18 – 22 Oct. 2010, CERN, Switzerland 6 1. Features of DDS Accelerating Structure –GLC/NLC

7. International Workshop on Linear Colliders, 18 – 22 Oct. 2010, CERN, Switzerland 7 1. Determination of Cell Offset From Energy Radiated Through Manifolds –GLC/NLC Refs: ?????? Dots indicate power minimisation

8. International Workshop on Linear Colliders, 18 – 22 Oct. 2010, CERN, Switzerland 8 DS Q cu RDDS1 ASSET Data Conspectus of GLC/NLC Wake Function Prediction and Exp. Measurement (ASSET dots) DDS3 (inc 10MHz rms errors) DDS1 RDDS1 H60VG4SL17A/B -2 structure interleaved Refs: 1. R.M. Jones,et al, New J.Phys.11:033013,2009. 2. R.M. Jones et al., Phys.Rev.ST Accel. Beams 9:102001, 2006. 3. R.M. Jones, Phys.Rev.ST Accel. Beams, Oct.,2009. 1. GLC/NLC Exp vs Cct Model Wake

9. International Workshop on Linear Colliders, 18 – 22 Oct. 2010, CERN, Switzerland 9 1) RF breakdown constraint 2) Pulsed surface temperature heating 3) Cost factor Beam dynamics constraints 1) For a given structure, no. of particles per bunch N is decided by the /λ and Δa/ 2) Maximum allowed wake on the first trailing bunch Wake experienced by successive bunches must also be below this criterion Ref: Grudiev and Wuensch, Design of an x-band accelerating structure for the CLIC main linacs, LINAC08 1. CLIC Design Constraints

10. International Workshop on Linear Colliders, 18 – 22 Oct. 2010, CERN, Switzerland 10 2.0 Initial CLIC_DDS Designs Three designs 1.Initial investigation of required bandwidth to damp all bunches (~3GHz) 2.New design, closely tied to CLIC_G (similar iris  a), necessitates a bandwidth of ~ 1 GHz. Geometry modified to hit bunch zero crossings in the wakefield. 3.Relaxed parameters, modify bunch spacing from 6 to 8 rf cycles and modify bunch population. Wake well- suppressed and seems to satisfy surface field constraints. CLIC_DDS_C (  f ~ 3.6 , 13.75%).

11. International Workshop on Linear Colliders, 18 – 22 Oct. 2010, CERN, Switzerland StructureCLIC _G Frequency (GHz)12 Avg. Iris radius/wavelength /λ 0.11 Input / Output iris radii (mm) 3.15, 2.35 Input / Output iris thickness (mm) 1.67, 1.0 Group velocity (% c)1.66, 0.83 No. of cells per cavity24 Bunch separation (rf cycles) 6 No. of bunches in a train 312 Lowest dipole ∆f ~ 1GHz Q~ 10 2.1 Initial CLIC_DDS Design –  f determination CLIC_DDS Uncoupled Design Bandwidth Variation  Variation CLIC_G 

12. International Workshop on Linear Colliders, 18 – 22 Oct. 2010, CERN, Switzerland 12  3.3 GHz structure does satisfy the beam dynamics constraints  However, it fails to satisfy RF breakdown constraints as surface fields are unacceptable.  8-fold interleaving employed  Finite no of modes leads to a recoherance at ~ 85 ns.  For a moderate damping Q imposed of ~1000, amplitude of wake is still below 1V/pc/mm/m 2. Initial design for CLIC DDS First dipole Uncoupled, coupled. Dashed curves: second dipole

13. International Workshop on Linear Colliders, 18 – 22 Oct. 2010, CERN, Switzerland 13 Uncoupled Coupled Q = 500 Amplitude Wake 2.2 Gaussian linked to CLIC_G parameters –Zero Crossings  Systematically shift cell parameters (aperture and cavity radius) in order to position bunches at the zero crossing in the amplitude of the wake function.  Efficacy of the method requires a suite of simulations in order to determine the manufacturing tolerances. Uncoupled params: /λ=0.102 ∆f = 3σ = 0.83 GHz ∆f/ = 4.56%

14. International Workshop on Linear Colliders, 18 – 22 Oct. 2010, CERN, Switzerland 14 Uncoupled parameters Iris radius = 4.0 mm Iris thickness = 4.0 mm, ellipticity = 1 Q = 4771 R’/Q = 11,640 Ω/m vg/c = 2.13 %c Iris radius = 2.13 mm Iris thickness = 0.7 mm, ellipticity = 2 Q = 6355 R’/Q = 20,090 Ω/m vg/c = 0.9 %c Cell 1 Cell 24 (f/ = 13.75 %) 2.3 Relaxed parameters tied to surface field constraints Cct Model Including Manifold- Coupling  Employed spectral function and cct model, including Manifold- Coupling, to calculate overall wakefunction.

15. International Workshop on Linear Colliders, 18 – 22 Oct. 2010, CERN, Switzerland 15 Structure Geometry Cell parameters a1 t/2 a L Iris radius Cavity radius Sparse Sampled HPT (High Power Test) Fully Interleaved 8-structures a min, a max = 4.0, 2.13 b min, b max = 10.5, 9.53 2.3 Structure Geometry: Cell Parameters b Rc a a+a1 R

16. International Workshop on Linear Colliders, 18 – 22 Oct. 2010, CERN, Switzerland 16 Avoided crossing Uncoupled 2 nd mode Uncoupled 1 st mode Uncoupled manifold mode Coupled 3 rd mode Light line 2.3 Relaxed parameters –full cct model Avoided crossing Uncoupled 2 nd mode Uncoupled 1 st mode Uncoupled manifold mode Coupled 3 rd mode Light line  Dispersion curves for select cells are displayed (red used in fits, black reflects accuracy of model)  Provided the fits to the lower dipole are accurate, the wake function will be well- represented  Spacing of avoided crossing (inset) provides an indication of the degree of coupling (damping Q) End Cell Mid-Cell Avoided crossing Uncoupled 1 st mode Uncoupled manifold mode Coupled 3 rd mode Light line Uncoupled 2 nd mode First Cell

17. International Workshop on Linear Colliders, 18 – 22 Oct. 2010, CERN, Switzerland 192 cells 8-fold interleaving 24 cells No interleaving 192 cells 8-fold interleaving Manifold Coupling slot Dipole mode Manifold mode ∆fmin = 65 MHz ∆tmax =15.38 ns ∆s = 4.61 m ∆fmin = 8.12 MHz ∆tmax =123 ns ∆s = 36.92 m ∆f=3.6 σ =2.3 GHz ∆f/fc=13.75% 2.3 Summary of CLIC_DDS_C Meets design Criterion?

18. International Workshop on Linear Colliders, 18 – 22 Oct. 2010, CERN, Switzerland 3. CLIC_DDS_E  Enhanced H-field on various cavity contours results in unacceptable  T (~65° K).  Can the fields be redistributed such that a ~20% rise in the slot region is within acceptable bounds?  Modify cavity wall  Explore various ellipticities (R. Zennaro, A. D’Elia, V. Khan)

19. International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 19 Circular Square Elliptical Convex Concave 3. CLIC_DDS_E Elliptical Design b a

20. International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 20 Circular Square ε=-8.28 ε=-4.14 ε=-2.07 Convex ellipticity Concave ellipticity Single undamped cell Iris radius=4.0 mm 3. CLIC_DDS_E Elliptical Design –E Fields

21. International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 21 CircularRectangularElliptical (Convex) Elliptical (Concave)  of cavity 1∞4.142.071.380.820.41-8.28-4.14-2.07 f acc (GHz)12.2412.0911.9812.011.9911.98 11.991111.991911.9935 Eacc(V/m)0.43 0.420.43 0.42 0.43 0.42 H sur max /Eacc (mA/V) 3.644.864.714.544.293.75 3 4.944.995.11 E sur max /E acc 2.27 2.332.28 2.33 2.27 2.33 Iris radius = 4. 0 mm Iris thickness = 4.0 mm 3 CLIC_DDS_E Elliptical Design, Single Undamped Cell Dependence of Fields on  Chosen design

22. International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 22 Optimisation of cavity shape for min Circular (  =1) Rectangular (  =∞) ε=4.14 ε=2.07 ε=1.38 ε =0.82 ε=0.41 Undamped cell Optimised parameters for DDS2 Circular cell ε=0.82 ε=1.38 Manifold-damped single cell 3. CLIC_DDS_E Single-Cell Surface Field Dependence on ε  Iris radius ~4mm. For both geometries  Averaging surface H over contour  =1.38

23. International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 23 Efficiency ∆f dipole ∆T P in  Optimisation of parameters based on manifold damped structures.  Vary half-iris thickness.  3-cell simulations, with intermediate parameters obtained via interpolation.  Choose parameters with minimal surface E-field, pulse temperature rise, and adequate efficiency. Chosen optimisation (CLIC_DDS_E) 3. CLIC_DDS_E, Optimisation of:, ∆f and Efficiency

24. International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 24 RcRc h r1r1 2*r 2 r2r2 h1h1 r 1 +h+2r 2 r1r1 a1 a2a2 g=L - t L a t= 2a 2 Radius = 0.5 mm Variable parameters (mm) Cell #1Cell#24 a4.02.3 b11.0110.039 a22.00.65 a1a22a2 Rc6.26.8 r23.252.3 Constant parameters (mm) All cells L8.3316 r10.85 h4.5 h11.25 Fillet @ cavity and manifold joint 1.0 Rounding of cavity edge 0.5 3. CLIC_DDS_E: Detailed Geometry

25. International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 25 ParameterDDS1_CDDS2_EModified to achieve ShapeCircularEllipticalMin. H-field (mm)2.352.65Min. E-field R c 1to 24 (mm)6.2-7.56.2-6.8Critical coupling DDS1_C DDS2_E 3. Impact on Parameters: CLIC_DDS_C to CLIC_DDS_E DDS1_C DDS2_E

26. International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 26 3. CLIC_DDS_E -Fundamental Mode Parameters DDS_E DDS1_C DDS_E DDS1_C DDS_E DDS1_C DDS_E Vg R/Q Q EsEs HsHs  Group velocity is reduced due increased iris thickness  R/Q reduced slightly  Surface field and  T reduced significantly by using elliptical cells

27. International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 27 DDS_C DDS_E 3. Wake Function for CLIC_DDS_E -Dipole Circuit Parameters DDS_C DDS_E DDS1_C ∆f=3.5 σ =2.2 GHz ∆f/f c =13.75% a 1 =4mm a 24 =2.3mm   Cct   Avoided Crossing   Avoided crossing  x is significantly reduced due to the smaller penetration of the manifold.  Some re- optimisation could improve this

28. International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 28 DDS1_C DDS2_E 3. Consequences on Wake Function Spectral Function Wake Function

29. International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 29 Rounding necessitates reducing this length (moves up) Rounding  To facilitate machining of indicated sections, roundings are introduced (A. Grudiev, A. D’Elia).  In order to accommodate this, R c needs to be increased  DDS2_ER.  Coupling of dipole modes is reduced and wake-suppression is degraded. How much? DDS2_E DDS2_ER RcRc 4. CLIC_DDS_E: Modified Design Based on Engineering Considerations  

30. International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 30 Light line Avoided crossing Uncoupled 2 nd Dipole Mode Cell # 1 Cell # 24 4. CLIC_DDS_ER Dispersion Curves Uncoupled Dipole mode Uncoupled manifold mode Cell # 1 Cell # 24 Light Line  

31. International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 31 CLIC_DDS_E :Rc=6.2 - 6.8 mm (optimised penetration)  CLIC_DDS_ER : Rc=6.8 mm const (a single one of these structures constitutes CLIC_DDS_A, being built for HP testing)  Wakefield suppression is degraded but still within acceptable limits. 4. CLIC_DDS_E vs CLIC_DDS_ER Wakefield Spectral FunctionWakefunction

32. International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 32  Info. on the ability of the 8-fold interleaved structure to sustain high e.m. fields and sufficient  T can be assessed with a single structure.  Single structure will be fabricated this year  CLIC_DDS_A, to fit into the schedule of breakdown tests at CERN. 4. CLIC_DDS_A: Structure Suitable for High Power Testing  Design is based on CLIC_DDS_ER  To facilitate a rapid design, the HOM couplers will be dispensed with in this prototype.  Use mode launcher design  Status: rf design for main cells complete, matching cells in mode launcher almost complete.  Mechanical drawings, full engineering design  EuCARD partners + CERN

33. International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 33 Cell # 1 Cell # 24 4. CLIC_DDS_A: Structure Suitable for High Power Testing  Non-interleaved 24 cell structure  High power (~71MW I/P) and high gradient testing  To simplify mechanical fabrication, uniform manifold penetration chosen Illustration of extrema of the end cells of a 24 cell structure

34. International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 34 4. CLIC_DDS_A Fundamental Mode Parameters

35. International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 35 Max. Values Esur=220 MV/m ∆T = 51 K Pin= 70.8 Eacc_UL=131 MV/m Sc=6.75 W/μm 2 RF-beam-eff=23.5% ∆T 35*Sc Esur Eacc Pin Dashed curves : Unloaded condition Solid curves: Beam loaded condition CLIC_G Values Esur=240 MV/m ∆T = 51 deg. Pin= 63.8 Eacc_UL=128 MV/m Sc=5.4 W/μm 2 RF-beam-eff=27.7% 4. HPT CLIC_DDS_A Parameters

36. International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 36 24 cells No interleaving 24 cells No interleaving Undamped Damped Q avg ~1700 4. HPT CLIC_DDS_A Wake

37. 37 International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland For each side of the structure (cell ♯ 1 and cell ♯ 24): We build a structure with one regular cell and two specular matching cell at its sides and we look at the minima S11 as a function of the geometrical parameters of the matching cells We do the same for a structure with two and three identical regular cells in the middle and still we look at minima S11 The matching condition is the one common to the three cases 4. Constant impedance matching

38. 38 International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland Beam Port 1 Port 2 E-fiel d 4. HPT CLIC_DDS_Full str. simulation 198.6326mm

39. 39 International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland S12 S22 S11 - 48.2dB@ 11.9944GHz V 26 [V]@P in = 1 W2678 G 26 [V/m]@P in = 1 W13481 P in [MW]@ 55.03 6165 @ 11.9944G Hz 4. HPT CLIC_DDS_Full str. simulation

40. 40 International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland Water pipes for cooling Vacuum flange Power input Power output Tuning holes Cut-view Bea m Thanks to Vadim Soldatov 4. CAD drawing : DDS_A

41. 41 International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland Profile accuracy

42. 42 International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland Surface finish

43. 43 International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 5. HPA (5π/6) Structure Power absorbed in the breakdown has quadratic dependence on the fundamental mode group velocity High Phase Advance (5π/6 ) operation will reduces the group velocity of the fundamental mode Hence the breakdown events in HPA structure are less likely expected compared to the standard (2π/3) structure

44. 44 International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 5.RF parameters as a function of v g

45. 45 International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 5.Kick factors for first six dipole bands

46. 46 International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 5. HPA dipole dispersion curves

47. International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 47 5. Spectral function Wake function

48. 48 International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland RF parametersUnitDDS_ADDS_HPA42DDS_HPA32 Phase advance / cellDeg.120150 Iris thicknessmm4/1.473.2/2.8 Bunch population10 9 4.2 3.2 Q (In / Out)-5020 / 65346931/7045 R’ (In / Out)MΩ/m51 / 11872.4/102.4 vg/c (In / Out)%2.07 / 1.02.1 / 0.45 Eacc max (L./UnL.)MV/m105 / 13293.3/ 14390/ 138 P in MW7168.263.6 ∆T max sur oKoK51 48 E max sur MV/m220234225 S c max W/μm 2 6.755.95.5 RF-beam efficiency%23.52923.3 5. Comparison 2π/3 Vs 5 π/6

49. 49 International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland  Better dipole damping  Low surface fields  Less in power required (low beam loading)  Need to improve dipole spread (at present 1.7 GHz)  Need to improve rf-beam-efficiency 5. HPA Summary

50. 50 International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 6. In progress 6.1 Enhanced damping :Eight manifolds Four regular and four additional manifolds Significant coupling

51. 51 International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland Cell parameters a = 4.3 mm t = 2.6 mm R c = 9.0 mm M r = 2.0 mm M c = 15.1 mm Fundamental mode properties Q=7080 R’/Q=10.356 (kΩ/m) v g =3.3 (%c) E s /E acc =2.22 H s /E acc =4.3 (mA/m) S c /E acc =5.45 x 10 -4 (W/μm 2 /Eacc 2 ) f syn =16.1 GHz Cell # 1

52. International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 52 Sic Iris radius = 4. 0 mm Iris thickness = 4.0 mm 6. In progress: 6.2 Lossy Manifold

53. 53 International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland Next step after CLIC_DDS_A is to provide for the “whole” structure which includes HOM couplers Studies are in a very preliminary phase The fundamental problem is to match the coupler in the whole first dipole band which goes roughly from 15.9GHz to 18GHz CLIC_DDS_B

54. 54 International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland A first qualitative result Polarization 2 Polarization 1 Freq=15.9GHz We do not care about it: it is well above cutoff Feeding 6. In progress: 6.3 DDS_B

55. 55 International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 1.V. F. Khan, et. al, A High Phase Advance Damped And Detuned Structure For The Main Linacs Of CLIC, LINAC10, 2010. 2.V. F. Khan, et. al, Recent Progress On A Manifold Damped And Detuned Structure For CLIC, IPAC10, 2010. 3.R. M. Jones, et. al, Influence Of Fabrication Errors On Wakefunction Suppression In NC X-Band Accelerating Structures For Linear Colliders, NJP, 11, 033013, 2009. 4.V. F. Khan and R.M. Jones, Investigation of An Alternate Means Of wakefield Suppression In The Main Linacs Of CLIC, PAC09, 2009. 5.R. M. Jones, Wakefield Suppression For High Gradient Lineacs For Lepton Linear Colliders, PRST-AB, 12, 104801, 2009. 6.V. F. Khan and R.M. Jones, An Alternate Design For CLIC Main Linac Wakefield Suppression, XB08, 2008. 7.V. F. Khan and R.M. Jones, Beam Dynamics And Wakefield Simulations For The CLIC Main Linacs, LINAC08, 2008. 8.V. F. Khan and R.M. Jones, Wakefield Suppression In CLIC Main Linacs, EPAC08, 2008. 9.R. M. Jones, et. al, Wakefield Suppression In A Pair of X-Band Linear Colliders, PRST-AB, 9, 102001, 2006. 7. List of Publications

56. International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 56 CLIC_DDS_A : A 2π/3 phase advacne single structure, is being fabricated (G. Riddone) and will be tested for high power performance ar CERN in 2011. CLIC_DDS_HPA : Is being studied for further optimisation by implementing additional manifolds and/or insertion of lossy material SiC. Summary

57. International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 57 I am pleased to acknowledge a strong and fruitful collaboration between many colleagues and in particular, from those at CERN, University of Manchester, Cockcroft Inst., SLAC and KEK. Several at CERN within, the CLIC programme, have made critical contributions: W. Wuensch, A. Grudiev, I. Syrachev, R. Zennaro, G. Riddone (CERN). Acknowledgements

58. International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 58 Extra Slides

59. International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 59 ∆a ∆t ∆b 4. CLIC_DDS_A Parameter Variation

60. International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland 60 4. CLIC_DDS_A Surface Fields

61. 61 International Workshop on Linear Colliders, 18-22 Oct 2010, CERN, Switzerland DDS_A